Photoelectric control



June 4, 1946. WOLFNER, 2 2,401,396

PHOTOELECTRIC CONTROL Filed Jan. 17, 1942 Patented June. '4, 1946 William F. Wolfner,.lI, Methuen, Masa, assignmto Photoswltch Incorporated, Cambridge, Mass., a corporation of Massachusetts Application January 17, 1942, Serial No. 427,209 12 Claims. (01. 256-415) This invention relates to electronic control circults and especially to arrangements where an energy impulse, derived for example from a phototube, has to initiate a given operation,- independently of the duration of the impulse.

Some of the main objects of the invention are to provide a circuit of this type which will respond instantaneously to changes in a controlling condition as for example light intensity, and to provide such a circuit "which retains a control organ in a predetermined state regardless of the duration of the impulse, either until a resetting operation is performed or during a predetermined time from the impulse.

Other objects are to provide such an arrangement which is very flexible and can easily be applied to various uses, and is simple and more rugged than arrangements heretofore used for this purpose. In another aspect, my circuit employs standard high vacuum tubes for functions usually assigned to gas tubes, with the advantages that it is cheaper and more certain in operation since gas tubes usually cost more, have shorter life, require more power, are less compact, and are more affected by uncontrollable influences as temperature or ionization effects, than are standard high vacuum tubes.

Equipment of this type is, for example, useful for controlling the feed of strip material to be cut in accordance with register marks regularly applied to the material, or for detecting random marks, for example seams or flaws of webs, the travel of the cloth being stopped when such a mark passes a predetermined point.

These and other objects, aspects and advantages will appear from the following description of two specific embodiments illustrating the genus of the invention by way of example and referring to a drawing, in which:

Fig. 1 is a diagrammatical representation of a cutting device incorporating the invention, including a control circuit; and

Fig. 2 a modification of the control circuit shown in Fig. 1.

In the embodiment of my invention to be described with reference to Fig. 1. the problem is to operate a cutting mechanism under the control of registration marks applied to strip material to be cut. Fig. 1 shows a table P supporting strip material W conveyed by suitable means (not shown because inessential) towards a cutting knife 20 which is normally held in raised position by a latch 2| engaging a lip 22 of the knife. An armature 23 is so connected to latch 2| that the knifeis released if magnet M3 attracts the armature. Suitable provisions are made for lifting the knife after each cutting operation; these are indicated in Fig. 1 as a solenoid M2 which lifts the knife when energized. It will however be understood that any apparatus which retracts the knife after each cutting operation will be satisfactory and that magnet M2 may for example be used to control more elaborate apparatus for that purpose. The knife 20 may also carry a finger 25 into whose path extends an actuator 26 or resetting switch S2. By means of this arrangement, switch S2 is opened for a moment, after the cuttingpperatlon has been performed. Retraction of the knife will not afiect switch S2. Means for supplying cutting force in addition to gravity are indicated by spring 21.

Registration marks m are applied to strip W, for example in the form of a dot or line printed on the strip and reflecting less light than the blank strip. These marks are supervised by means of a scanning lantern L directing a light beam 1 towards the strip W, which reflects it towards a phototube T4 constituting a detecting impedance. 'I'hephototube is suitably mounted in relation to lamp L and strip W so that the intensity of the light flux reaching the tube is varied by the interposition of the registration marks m. It will be evident that other markings as for example perforations blocking or transmitting a light beam could be used.

As will be described in detail below, changes of the illumination of the phototube due to the passing of marks cause knife 20 to drop and to cut off blank W, to actuate resetting switch S2 and to be retracted into position for the next cut, the spacing of cuts being regulated by the distance of the marks passing lamp L. The circuit controlling this operation will now be described.

A current source, for example a standard alternating current line indicated by terminals I, 2 is connected to primary II of transformer if having a rectifier secondary l2, and an auxiliary secondary l3 for supplying the heater elements of the 3 placed by two individual matched tubes) having sections I and II with anodes aI, aII, cathodes k1, MI, and control electrodes gI, gII, respectively, is connected between busses 3 and 4 as follows. Three resistors RI, R4 and R5 of suitable dimensions are connected in series between wires 3 and 4; anode a1 is connected between RI and R4, and grid gII to a point 8 between R4 and R5. Three corresponding resistances R2, R3 and R8 are connected between 3 and 4, in series with relay magnet MI constituting operator means responsive to the current conducted by section II of tube T2C. Anode an is connected to a point between R2 and R3 and grid gI to point 3 between R3 and R8. Cathodes Id and 1011 are connected through resetting switch S2 and to wire 4, in the manner to 'be described below. I

A pentode TI, constituting electronic actuator means, has an anode al which is connected to point 3; the cathode kl is joined to point 6 between a resistance RI I and a potential apportioning'resistance RI2 connected in series to a point 5 which is also connected to cathode kI, and terminal 4. The grids of the pentodes are connected to a control network N comprising resistors R1, R8, R9 and condensers CI, C2 arranged as follows. Resistances R9, R8, condenser CI and resistance R1 are connected in series between point 6 and adjustable tap of potentiometer I2. Control grid .0 is connected to the low potential side of condenser CI, screen grid s to point 5 and suppressor u is connected to point 6, if desired through a normally closed switch at, z. Condenser C2 is connected between wire 4 and a point between RB and R9.

Anode 14 of phototube T4 is connected to the high potential side of condenser C I, whereas cathode k4 is connected to wire 4.

A condenser C3 may be connected between H and 4; condenser C4 bridges magnet MI in the customary manner.

Switch SI normally energize magnet M2 through contact 22, with MI deenergized, whereas magnet M3 is energized through contact 2| if magnet MI carries current.

This arrangement operates as follows.

Rectifier arrangement 3-T3-4 is normally operative and will impress a direct current voltage upon terminals 3, 4, rendering 3 for example 300 volt positive relatively to 4. Tube T2 passes a steady current through one or the other of its anodes; under normal conditions, that is with knife 20 raised, section I conducts. This current passes through RI, RI I, RI 2, rendering point 5 positive relatively to 4, for example 150 volt. Resistances R4 and R5 are equal so that grid 911 is negative, for example to the amount of about 50 volt, with regard to its cathode kII which is normally connected to point 5 through switch S2. Hence, section II of tube T2 is at this time nonconductive so that there exists no voltage drop through MI and R2. Resistors R3 and R5 being equal, the potential of grid 91 is about one-half the potential difference between wires 3 and 4, that is about 150 volt positive relatively to 4. Since the voltage at 5, which is connected to kII, is likewise about 150 volt, the net bias of grid gI is zero, tube T2 being conductive through section I as assumed.

If the voltage of grid gI is reduced by a control instrumentality, the current and hence the voltage drop in RI and the bias of gII are reduced, so that tube T2 becomes conductive through section II and a voltage drop is produced in MI, R2 which further increases the negative bias 0! gI,

promoting the eifect of the control instrumentality which has initially lowered the potential of grid 91. Section II is now as stably conductive as section I was before the potential of 91 was lowered. It will be evident that magnet MI will be energized with section II conductive, whereas the current through RI I, RI2 to which the cathodes are connected, is essentially constant regardless of the fact whether section I or II conducts, assuming that switch S2 is closed.

If switch S2 is opened, cathode kII will lose its potential and section II become nonconductive so that the current drop across MI R2 disappears, the potential at 3 and g1 raises, and conductivity is restored to section I.

Condenser C3 has the purpose of by-passing the voltage network RI I-RI 2 for eliminating the effect of transients occurring during the change of conductivity from I to II, so that the current flow in RI I, RI2 is quite uniform and the potential at 5 undisturbed by this change in tube T2.

With section I conductive, the potential of grid a1 is lowered and conductivity transferred to section II energizing MI, by means of phototube T4 as follows.

Under normal conditions, that is. with knife 20 raised and section II of tube T2 nonconductive, the potential of point 3 is almost that of terminal 3 because there is no drop across MI and R2, and tube TI is ready to conduct. The bias of control grid 9, however, is normally set by tap I on potentiometer RI2 to render tube TI normally nonconductive.

Condenser CI maintains an average direct voltage value equal to the difference between the grid voltage at I and g and the voltage at 8 as modified by any voltage drop in R8. The voltage drop in R8 is affected by the conductivity of phototube T4 which, with decreasing illumination of k4, will conduct a decreasing current through circuit 3-T25RI I-6--R9-RB--a4k4-4. Condenser C2 acts as a filter to remove transients or alternating current ripples from the supply voltage of the phototube.

The time constant of network 6R3--R5 CI-R'II is so chosen that the grid voltage of TI i not affected by slow variations of the impedance of the phototube due for example to changes of ambient illumination, but if a sudden decrease of illumination and hence increase of the impedance of T4'takes place, the consequent current reduction in R8 will reduce the voltage drop across RB and if the time constant of network N is so chosen that Cl can not discharge so fast as this potential drop tends to decrease, the potential at the low potential side of CI and hence at y will rise and tube TI become conductive in circuit 3MIR2-R39-TI-6. This causes a voltage drop in R3, lowerin the potential of point 3 below the critical voltage of grid g1 and transferring the conductivity of tube T2 to section II and energizing MI as above described.

Summing up, with knife 20 in readiness for cutting, tube T2 conducts through section 1, MI is deenergized, switch contact 2I open and contact 22 closed. Tube TI derives sufiiciently negative grid bias from RI2 to be nonconductive, and average illumination affects phototube T4 with changes slow enough so that condenser CI discharges through network N before the bias of g can be affected sufliciently for an appreciable change of the conductivity of tube TI. If the light on T4 is suddenly decreased by a mark m absorbing the light of beam 1, the current in opened, which latter will be so set in the present instance that normal condition is restored as above described so soon as knife 2| has penetrated the strip.

If it is desired to prevent restoration to normal condition, suppressor screen u of tube Tl, instead of being permanently connected to the cathode at y, 2, may at y be joined temporarily with appropriate switch gear to an auxiliary circuit which renders it sufliciently negative to preventTl from becoming conductive, regardless of energy impulses coming from phototube Tl. This arrangement thus provides means for blocking and unblocking the conductivity of tube Tl, the electronic actuator means.

This use of the suppressor-as a control electrode permits supervision of the cutting operation independently of the register marks; the effect of the marks can be in this way eliminated for any part of the operating period, as for example during periods selected at will by the operator, or cyclically in order to render certain selected marks ineffective.

It will be evident that the resetting operation, instead of being automatically derived from the operating element as knife 20. can be performed by closin switch S2 manually, as may for example be preferable if marks to be detected are irregularly spaced at longer intervals, as for example if it is desired to detect and to eliminate faulty pieces in strip material, as webs, in which case magnet M3 may operate a device for stopping the web conveyor enabling the operator to take the necessary steps; in that case means for restarting the conveyor may be connected with manually operated switch S2.

, 6 l-Tl-Rl-J increases, the voltage of 0 goes more positive and tube Tl becomes conductive. Again, conductivity is transferred to section 11 due to the above explained motion of TI. a d a! being driven negative due to the voltage developed across magnet MI and the adjacent section of RIB. The condition is therefore the same as in Fig. 1 with section II conducting and point 9 driven negative. Here, however, condenser Cl will discharge through resistor RI and after a suliiciently long time period. depending on the electrical values of this timing circuit, grid 91 If it is desired to make the resetting operation independent of the ultimate function of the apparatus. an arrangement similar to that shown in Fig. 2 may be used.

Fig. 2 shows certain elements of the electric circuit according to Fig. l, with the following tentiometer RIS. The positions of phototube T4 and resistor R8 are interchanged for operation responsive to sudden increase of the illumination of the phototube. The rest of the circuit is similar to that of the first embodiment as indicated by the numerals designating corresponding elements of Figs. 1 and 2.

The circuit according to Fig. 2' operates as follows.

Upon the circuit attaining normal conditions with section I of tube T2 conducting, condenser Cl will charge due to grid current through section I, approximately to the potential difference between 5 and 3, as for example about 150 volts. when the illumination of phototube T4 is suddenly increased, the impedance of the tube decreases correspondingly, the current in circuit will no longer be sufl'lciently negative to prevent current flow through section I. This section will again become conductive and magnet Ml. deenergized; Cl will charge again and the circuit is ready for the next cycle of operation, as for example initiated by a mark passing beam 1.

By means of potentiometer RIS, the time after which the circuit automatically resets itself may be varied over wide limits, the maximum value being determined by resistor RI.

Tube Ti will advantageously be a high mu pentode which should work into a high plate impedance in order to have sufficient gain, whereas tube T2 works well with comparatively low load impedance promoting a plate current sufliciently high to operate the relay magnet. These requirements are met by magnet Ml which is in the anode circuits of both tubes and has clue to its magnetic circuit a high impedance for short load impulses of tube Tl whereas it has a comparatively low resistance in the direct current load circuit of tube T2.

Summing up, in the circuit according to Fig. 2 an impulse from the phototube causes section II to become conductive, energizing magnet MI and operating an instrumentality corresponding to M3. Thi condition continues regardless of the duration of the impulse, for a given period of time determined by the setting of Hi5 and the value of RIG. At the end of this period section II becomes again nonconductive and magnet Ml deenergized.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. Electric control apparatus comprising electronic relay means having two anode means, two electrode means arranged for controlling electron flow to respective anode means, and cathode means carrying a. substantially constant current through one or the other of said anode means dependent upon the potential difierences between said control electrode means and said cathode means; current responsive operator means connected to the first one of saidanode means; potential apportioning mean connected to said cathode means; electronic actuator means comprising anode, cathode and control grid; means controlled by the conductivity of said actuator I means for varying the potential diiference between said cathode means and said first control electrode means and shifting conductivity to said other anode means; a network comprising two impedances connected in serie between two points of higher and lower potential, respectively, derived from said apportioning means; and a condenser inserted between the connection point of said impedances and said grid; one of said impedances being a phototube whose impedance changes vary the potential of said connection point and said grid and hence the conductivity of said actuator means .and-the response of said operator means, dependent upon the discharge of said. condenser through said network.-""

2. Electric control apparatus comprising electronic relay mean having two anode means. two electrode means arranged for controlling electron now to respective anode means, and cathode means carrying a substantially constant current through one or the other of said anode mean dependent upon the potential differences between said control electrode means and said cathode means: current responsive operator means connected to the first one of .said anode means; potential apportioning means connected to said cathode means; electronic actuator means comprising anode, cathode and control grid: means controlled by the means for decreasing the potential difference between said cathode mean and said first control electrode means with increasing conductivity of said actuator means and shifting conductivity to said other anode means; a network comprising two impedances connected in series betweentwo points of higher and lower potential, respectively, derived from said apportioning means; a condenser inserted between the connection point of said impedances and said grid; one of said impedances being a phototube whose impedance deviation from a normal value raises the potential of said connection point and said grid and hence the conductivity of said actuator means, and the response of said operator means dependent upon the discharge of said condenser through said network; and means for again increasing said potential difierence after a predetermined time and shifting conductivity back to said first anode means.

3. Electric control apparatus comprising electronic relay means having two anode means, two electrode means arranged for controlling electron flow to respective anode means, and two cathode means; means for normally connecting said cathode means to each other, a substantially constant current being carried through one or the other of said anode means dependent upon the potential differences between said control electrode means and the connected cathode means; currentresponsive relay operator means connected to the first one of said anode means; mean connected to the first one of said cathode means for supplying both cathodes when connected: actuator means for varying the potential difierence between said first cathode means and said first control electrode means and shifting conductivity from one to the other anode means and hence controlling the response of said operator means; and means for disconnecting said cathode means from each other thereby shifting conductivity back to said first anode means.

4. Electric control apparatus comprising electronic relay means having two anode means, two electrode means arranged for controlling electron flow to respective anode means. and two cathode means; means for normally connectin said cathode means to each other, a substantially constant current being carried through one or the other of said anode means dependent upon the potential difierences between said control electrode means and the connected cathode means; current responsive relay operator means connected to the first one of said anode means; means connected to the first one of said cathode nected; actuator means for varying the potenmeans for upplying both cathodes when contial difference between said first cathode means and said first control electrode means and shifting conductivity from one to the other anode means and hence controlling the response of said operator means; and means controlled by said operator means for disconnecting said cathode mean Irom each other thereby shifting conductivity back to the first anode means upon response of said operator means.

5. Electric control apparatus comprising electronic relay means having two anode means, two

electrode means arranged for controlling electron flow to respective anode means, and cathode means carrying a substantially constant current through one or the other of said anode means dependent upon the potential differences between said control electrode means and said cathode means; current responsive operator means including an inductance with magnetic circuit connected to the first one of said anode means; electronic actuator means comprising anode, cathode and control grid; and a connection from said anode to said inductance and to the electrode means controlling the other anode means, a sudden current increase in said connection due to suddenly increased conductivity of said actuator means increasing the voltage drop in said inductance, lowering the voltage of said first control electrode means and shifting conductivity to said other anode means.

6. Electric control apparatus for initiating a given operation in response to an energy impulse, comprising an electronic relay device having two control electrodes and two output circuit branches with a common portion, each branch being part of a potential apportioning circuit that supplies said output circuits and said control electrodes of the other output branch, an operator relay in one of said output branches, a supervising network supplied with constant voltage and adapted to vary the potential distribution in said apportioning circuit of said output branch with the relay and hence the control potential of the other output branch which potential variation shifts conductivity from one to the other output branch, and an operation conditioned switch for separating said first output branch from said common portion, whereby momentary response of the network shifts the energizing conductivity to the first output branch and actuation of the switch shifts conductivity back to the other output branch which retains the first output branch nonconductive until the network again responds while said switch is closed.

7. Apparatus according to claim 6 wherein the said network is supplied with constant voltage from said common portion which carries practically constant current while conductivity shifts from one branch to the other.

8. Apparatus according to claim 6 wherein said supervising network comprises a time delay circuit including a condenser adapted to be charged proportionate to said constant voltage and an amplifying tube feeding into a load impedance controlling the control electrode of said other output branch, the low potential side of the condenser being also connected to the control electrode of said amplifying tube and the high potential side of the condenser being also connected through a supervising variable conductor to a low potential point of said network, sudden decrease of the current through the variable conductor raising the potential of the low potential tronic relay means having an output circuit with anode means and cathode means, and grid means, and operating with substantially constant current in a portion of said output circuit; current responsive operator means and potential apportioning means connected in said portion; electronic actuator means having anode, cathode and control electrode; a network including in series connection, the anode and cathode of said actuator means and a portion of said potential apportioning means whereby said actuator means is supplied with a substantially constant plate potential; a capacitance'and-a resistance connected in series to said potential supply points; a connection from one side of said capacitance to said electrode; and control means for varying the voltage drop in said resistance and hence the potential of said electrode and the conductivity of said actuator means.

10. Electric control apparatus comprising electronic actuator means having anode, cathode and two control electrodes, means responsive to the conductivity of said actuator' means, a current source, a network having two points supplying from said source a substantially constant voltage, two impedances connected in series between said points, a capacitance inserted between the connection point of said impedances and one of said electrodes, a circuit for the discharge of said capacitance, one of said impedances being variable and adapted to change the potential of said connection point and 01' said electrode and hence the conductivity of said actuator means dependent upon said discharge, and means in circuit with said second electrode for blocking and unblocking the conductivity of said actuator means.

11. Electric control apparatus comprising electronic relay means having anode means, cathode means and grid means and supplying substantially constant current, current responsive operator means connected to said anode means, potential apportioning means supplied by said relay means with substantially constant current, electronic actuator means having anode, cathode and two control electrodes, means responsive to the conductivity of said actuator means, a current source, a network having two points connected to said apportioning means for supplying therefrom a substantially constant voltage, a capacitance connected at one side to one of said electrodes, a resistance connected between the other side of said condenser and said supply point of higher voltage, a phototube connected between said other side and said other supply point,'a circuit for the discharge of said capacitance, darkening of said phototube and increase of its impedance raising the potential of said other condenser side and the potential of said electrode, dependent upon said discharge, and means in circuit with said second electrode for blocking and unblocking the conductivity of said actuator means.

12. Electric control apparatus comprising electronic relay means having anode means, cathode means and grid means and supplying substantially constant current, current responsive operator means connected to said anode means, potential apportioning means supplied by said relay means with substantially constant current,

electronic actuator means having anode, cathode and two control electrodes means responsive to the conductivity of said actuator means, a current source, a network having two points connected to said apportioning means for supplying therefrom a substantially constant voltage, a capacitance connected at one side to one of said electrodes, a resistance connected between the other side of said condenser and said supply point of lower voltage, a phototube connected between said other side and said other supply point, a

circuit for the discharge of said capacitance, il-

lumination of said phototube and decrease of its impedance raising the potential of said other condenser side and the potential of said electrode, dependent upon said discharge, and means in circuit with said second electrode for blocking and unblocking the conductivity of said actuator means.

WILLIAM F. WOLF'NER, II. 

